Selective oxidative dealkylation



March 1965 c. J. NORTON ETAL 3,175,016

SELECTIVE OXIDATIVE DEALKYLATION Filed March 20, 1961 6 Sheets-Sheet lPRESSURE CONDENSER PRESSURE 0- RELIEF VALVE WATER CONDENSER REF LUX) 5gcoagggr ms AFFEL I m i; REACTOR P AIR FEED 3 5 1 g: gl g N N E! 5% 3 7WET TEST s! 6 3 'ELT-C-I 5:. \7 DRY ICE TRAPS m: I 3i Fla-I FLUID-BEDREAcmR INV ENT OR.

CHARLES J. NORTON BY THURLE E.MOSS

ATTORNE YS March 1965 c..:. NORTON ETAL SELECTIVE OXIDATIVE DEALKYLATION6 Sheets-Sheet 2 Filed March 20, 1961 gma an :4 32 89 31 es- 3 0 3:532:30 282 3 :4 M a WIWH. 22 g a 3% m 8030A- aa-um 38 Ann Sa 3 2 2% 2.289:95 55.30

SEES-om C IN VEN TORS CHA RL ES J. NORTON THURLE E. MOSS ATTORNEYS March1965 c. J. NORTON ETAL 3, 7

SELECTIVE OXIDATIVE DEALKYLATION Filed March 20, 1961 e Sheets-Sheet :5

Theoretical Limit 100 PERCENT NAPHTHALENE IN PRODUCT I I I I l I I I I II I I I I I I I I I I I I I I I 16 PERCENT COMBUSTION 0F FEED FIG. 3CATALYSTS FOR OXIDATIVE DEALKYLATIQN INVENTORS CHARLES J. NORTON THURLEE. MOSS AT TORNEYS March 1965 c. J. NORTON ETAL ,9

SELECTIVE OXIDATIVE DEALKYLATION Filed March 20, 1961 6 Sheets-Sheet 4 mg 90 Over 3.4 Wt. Gadmia-silica Catalyst g 80 e-i K E 10|ln 29 02 5'3 0REACTION TEMPEATURE,

IN V EN TOR-S CHARLES J. NORTON THURLE E. MOSS BY ATTORNEYS March 1955c. J. NORTON ETAL 5,

SELECTIVE OXIDATIVE DEALKYLATION Filed March 20, 1961 6 Sheets-Sheet 5 02-) a \d l 8553- ZE$OURS fr, l.0 LOG [wT CdO] 'HASE Oxmmow IF 1- IVERCADMIA AT 400C ELECTHVE VAPQR- Ki} 2 it} 21 E E Q h Li INVENTORS CHARLESJ. NORTON THURLE E. MOSS ATTORNEYS March 1965 c. J. NORTON ETAL3,175,916

SELECTIVEOXIDATIVE DEALKYLATION Filed March 20, 1961 e Sheets-Sheet eISOYIELD CONTOURS FIG, 6 SELECTIVE VAFm; l T0 APMHALENE INVENTORS.CHARLES J. NORTON BY THURLE E.MOSS

ATTO RN E YS United States Patent 3,175,016 SELECTIVE OXIDATIVEDEALKYLATION Charles J. Norton and Thurle E. Moss, Denver, Colo,assignors to The Marathon Oil Company, Findlay, Ohio, a corporation ofOhio Filed Mar. 20, 1961, Ser. No. 108,688 Claims. (Cl. 260-672) Thisinvention relates to the controlled selective vapor phase oxidation ofalkyl substituted hydrocarbons to lower molecular weight hydrocarbons,and more particularly is directed to the control selective vapor phaseoxidation for the dealkylation of alkyl substituted aromatichydrocarbons to lower weight homologs of these compositions andspecifically to produce the more desirable parent homolog of suchcompositions.

Any mixed hydrocarbon material, whether derived from petroleum, coaltar, shale oil, and similar materials, invariably includes in such amixture a substantial portion of higher molecular weight homologs andderivatives of various of the hydrocarbon compositions, including suchcompositions as paraffins, olefins, aromatics and the like. Theconventional recovery of aromatic hydrocarbons from such materials,whether the stream or mixture is a virgin or a processed stream ormixture, invariably includes a substantial amount of alkylaromatichomologs of the parent aromatic hydrocarbon, as well as otherderivatives such as alkylhydroaromatic hydrocarbons of the monocyclic,bicyclic, or polycyclic homologous series. With treated streams, forexample, treatments such as thermal cracking, catalytic cracking,hydro-forming, hydrocracking, etc., substantial amounts of alkylaromaticand alkylhydroaromatic hydrocarbons are found in the resultant mixtures.

The predominant homologous aromatic hydrocarbon series in a productstream depends upon the nature of the original stream, the treatmentprocess and the severity of the treatment of the original stream.Furthermore, in most cases these streams are frequently richer in thehigher molecular weight homologs or derivatives than in the parenthomolog itself. Normally, such streams include a large number ofisomers, at relatively low concentration each, which greatly complicatesthe separation, purification, utilization and marketing of individualmembers of the stream. For such reasons alkylaromatic hydrocarbons havenot been as valuable commercially as the parent homologs, for example,benzene naphthalene, anthracene, etc., have been commercially morevaluable as chemicals than their alkyl homologs.

The oxidation of hydrocarbons to oxygenated reaction products is wellknown in literature. Examples of such include the oxidizing olefins toepoxides, glycols, aldehydes, acids, etc., over various catalysts;alkanes have been oxidized by air or oxygen in the vapor phase, in theabsence of catalysts, to mixtures of valuable oxygenated derivatives;naphthalene, methylnaphthalenes, phenanthrene, anthracene, tetralins andxylenes have been catalytically oxidized in the vapor phase overcatalysts such as vanadium, molybdenum oxide, tungstic oxide, andvarious other mixed metallic oxides to phthalic anhydride, maleicanhydride, and/ or naphthoquinone, depending upon the composition of thefeed mixture. Likewise, it has been known to oxidize naphthalene andortho-xylene to phthalic anhydride over fixed or fluid bed vanadia;benzene and toluene have been oxidized to maleic anhydride, and tolueneoxidized to benzyl alcohol, benzalde hyde and benzoic acid underslightly diiTerent conditions.

In the known oxidation processes of aromatic hydrocarbons, carbondioxide, water, maleic anhydride, phthalic anhydride, naphthoquinone,and naphthol have been iso- 3, l 1 h Patented Mar. 23, 1965 lated asreaction intermediates or products from methylnaphthalene andnaphthalene feed materials.

According to the present invention we have prepared naphthalene as aproduct from the oxidation of methylnaphthalene and have furtheroxidized other organic materials such as peroxide, ethers, alcohols,aldehydes, acids and esters, in the vapor phase under highly selectiveconditions to the parent hydrocarbon. Additionally, we have discovered ahighly eificient two-step oxidation of methylnaphthalene to phthalicanhydride. By controlling the reaction conditions in relation to theparticular catalyst, the oxidation according to the invention mayproduce naphthalene as a major reaction product from alkylnaphthalenes.

Included among the objects and advantages of the present invention is aselective oxidation process for the dealkylation of alkylaromatichydrocarbons by controlled selective vapor phase catalytic oxidationover fluidized oxidation catalysts. The process provides a novel,efficient and economical method for the oxidative dealkylation of higherhomologs in an alkylaromatic hydrocarbon series to lower molecularweight compositions and to the parent homolog of the series. Theinvention, furthermore provides a novel catalyst system for oxidativecatalysis of various hydrocarbon systems.

Further objects and advantages of our invention relate to a novelprocess for producing parent homologs of aromatic hydrocarbons as wellas a two-step vapor phase oxidation of certain aromatic hydrocarbonmixtures for the improved production of phthalic anhydride, maleicanhydride, and naphthoquinone. The process of the invention includes anefficient and effective process for producing naphthalene from variouspetroleum streams containing varying amounts of alkylnaphthalenes, andcertain hydrocarbon streams enriched in alkylnaphthalenes derived fromvarious refinery streams, whether virgin or treated steams.

Additional objects and advantages reside in the process for producingnaphthalene from light catalytic cycle oil cuts which may be oxidizedper se or from extracted portions which are selectively enriched inalkylaromatics.

Still other objects and advantages of the invention reside in modifyingthe conditions of oxidative cracking of hydrocarbon streams by theaddition of controlled amounts of gaseous oxygen such as air and oxygen.Sulfur oxides and nitrogen oxides may be added to exert beneficialcracking effects far out of proportion to their stoichiometry and atreaction conditions of considerably less severity.

Additional objects and advantages will be readily apparent from thefollowing description.

In producing the parent homolog of aromatic series, the feed materialused for the oxidative cracking determines the ultimate products.Various types of feed materials may be used in the process andcompositions such as alkylheterocyclic aromatic hydrocarbons may beoxidatively dealkylated to lower molecular weight homologs, similarly,organic derivatives such as alcohols, aldehydes, acids, ethers, esters,peroxides, etc. may be oxidatively reduced to the parent compound. Inaddition, crude mixtures containing the alkylaromatic hydrocarbons maybe oxidatively reduced to produce the parent compound, and in onepreferred process the aromatic hydrocarbons in a light catalytic cycleoil are selectively extracted from the oil to produce a hydrocarbon feedfor the process.

Numerous materials may be employed as effective catalyst for theoxidative cracking. The principal metal oxides for catalysts may be oneor more of the oxidation states of one or more of the metals of theperiodic chart groups 1B, 113, I113, IVB, VB, VIB, VIII, IIIA, IVA,

VA and VIA, are preferably of the periodic groups IB, IIB, IIIA, IVA andVA, for example, silver, zinc, cadmium, mercury, aluminum, gallium,indium, thallium, silicon, germanium, tin, lead, bismuth, etc.Especially good selective activities were found for the oxides ofsilver, zinc, cadmium, indium, and bismuth. Surprising- 1y, cadmiumcompositions, and especially amorphous cadmium oxide, were found to behighly selective in the oxidative cracking process. In addition,compounds of cadmium and other metals of the group have been found to behighly selective, for example, cadmium silicate was highly selective inoxidative cracking.

The catalysts specified above may be modified by activators which may bechosen from the less selective but more active metal compounds of groupsenumerated above, for example, chromium, manganese, iron, cobalt,nickel, and copper oxides. In addition, inihibitors under someconditions may be used to control the activity of the catalyst, andthese may be chosen from various of the metal oxides or compounds ofmetals and non-metals in groups IA, IIA, IIIB, IIIA, and stable oxidesor anions derived from the metals and non-metal groups IIIA, IVA, VA,VIA and VIIA under the reaction conditions. Such inhibitors or modifiersmay also be alkali or alkaline earth metal salts of stable aluminates,silicates, phosphates, sulfates, for example, sodium, lithium orpotassium sulfate, acid sulfate, or phosphate.

Such catalysts may be used alone or on a catalyst base, and it ispreferably used as a fluidized catalyst bed. Such fluidized catalystbeds are well known in the art, and in general such beds includeproviding the catalyst material in small sizes and maintaining thecatalyst in a fluid state by means of passing the vaporized hydrocarbonfeed and air through the bed at a sufficient velocity to maintain thecatalyst material suspended in the air.

The catalysts for use according to the invention should be dried andpreactivated in air or oxygen at a temperature of about 500-600 F. for asuitable time. Spent catalyst may be regenerated under similarconditions. To maintain a continuous catalytic oxidative crackingreaction using recycled catalyst, the regeneration rate of the spentcatalyst must be faster than the oxidative cracking rate so that thecatalyst may be withdrawn, regenerated, and recycled into the reaction.This maintains the catalyst in a highly reactive state.

Supports for the various catalysts may be conventional catalystsupports, for example, alumina, silica, silicaalumina, silicon carbide,boria, beryllia, glass, ceramic material, etc. Generally, a relativelyinert support is most desirable, since, under some conditions strongabsorption of hydrocarbons by the support reduces good selectivity fordiscriminate oxidation between the feed and the product hydrocarbons.For example, activated chromatographic grades of alumina and silica gelabsorb hydrocarbons very strongly and, unitl the materials arecompletely saturated with the hydrocarbons at the temperature of thereaction, no oxidation product is recovered. Fused alundum, some of theless porous and less absorbent silicas, alumina, and silica aluminas,and like material provide good support material. Amorphous silica gelprecipitated by acidification from sodium silicate solution is anexcellent support.

Equipment for the process of the invention may be suitable apparatus foreither fluidized or fixed bed catalysis, and both types are known inmany forms. One fluid bed reactor which is highly suitable for theprocess of the invention is shown in FIG. 1.

In conducting the selective oxidative cracking of the invention, it ishighly important to maintain a close control on the temperature of thereaction so as to prevent the oxidation from proceeding beyond thedesired dealkylation or" the aromatic hydrocarbons. The oxidativecracking of the invention proceeds rapidly and at a considerably lowerreaction temperature than catalytic or thermal hydrocracking, and thecontact times required for the catalytic and thermal hydrocracking aremany times greater than for the oxidative cracking according to theinvention. Uncontrolled oxidation, obviously, may proceed to completeoxidation with the production of carbon dioxide and Water, which isdetrimental where the desired product is a parent aromatic homolog.

The reaction of the invention is conducted at closely controlledtemperatures. A low air-to-feed ratio is necessary to obtain optimumproduction of the parent aromatics or other lower molecular weight fromthe higher homologs. Good selective oxidation conditions may be obtainedin the region of from BOO-600 C. with a contact time of 0.05 to 1.0seconds and, with an air feed ratio of 0.1 to 10 liters of air per gramof feed. Preferably, the temperature range is 400450 C. with up to about10 weight percent of catalyst, and from about 5-25 weight percentogygen.

The most convenient and practical gaseous oxidant is air. However, ithas been demonstrated that the concentration of oxygen in the initialoxygen bearing stream is an important reactant variable which aiTectsthe selectivity of the oxidation. For certain applications theconcentration of the gaseous oxidant in the gaseous phase may be variedfrom about 0.1% to nearly pure oxygen. Inert diluents, such as nitrogen,rare gases, carbon dioxide, carbon monoxide, and even water vapor may beadded in controlled amounts to favor the oxidation selectivity. Thepressures under which these reactions maybe effected range from about0.1 to 1000 atmospheres with the practical range in 1 to 10 atmospheres.

In one form of the invention the oxidation process is conducted bypassing a stream of vaporized hydrocarbon feed vertically upwardlythrough a column containing either a fixed bed or a fluid bed catalyst.The air-hydrocarbon feed rates are closely regulated by conventionalmeans, and these are preheated to approximately the temperature of thedesired reaction. The rate of feed of hydrocarbon and air is determinedby the size of the column so as to limit the residence time of thehydrocarbon in the reactor to within a preferred contact time rangedepending on the particular catalyst.

Exemplary apparatus and oxidation results are shown in the appendeddrawings in which:

FIG. 1 is one form of a fluid bed oxidation catalyst apparatus;

FIG. 2 is a modified form of a fixed bed oxidation apparatus;

FIG. 3 is a graph showing the activity of three catalysts in producingnaphthalene from l-methylnaphthalene;

FIG. 4 is a graph showing the effect of temperature on a feed with twomixtures of gas containing different amounts of oxygen; and

FIGS. 5 and 6 are charts showing isoyield and isoconversion contours ofnaphthalene from l-methylnaphthalene made by plotting the logs ofCadmium oxide concentration and oxygen concentration at 400 C. and 450C., respectively.

In the form of the apparatus shown in FIG. 1 it consists of a tubularstainless steel reactor 1 having a lower inlet 2 for admission of airand hydrocarbon vapor, and an upper outlet 3 leading into a condensingtrain 4. The reactor provides a volume 5 in its upper portion which isof a larger cross-sectional dimension than the vertical column forcatalyst disengaging, and in one form it has about a cross-section ofsix times the cross-sectional area of the lower zone 6, which is thereaction zone. This catalyst disengaging zone facilitates the settlingof the catalyst from the vapor. A porous stainless steel disc 7 in thebottom of the reactor zone provides a catalyst support to prevent itfrom falling back through into the bottom of the reactor. This disc issufficiently porous to provide only a small restriction in the fluidflow therethrough. Four pressure taps P P P and P are connected topressure meters, for example, mercury-filled monometers (not shown) formeasuring pressures in various parts of the reactor. In addition, bycomparing the overpressures of the diiferent points in the reactor bed,it is possible to calculate the pressure drop across the catalyst bedand hence follow the extent of fiuidization. A porous stainless steelbayonet filler 9 covering the upper outlet, essentially preventscarry-over of catalyst into the condenser system. The reactor issuitably heated by wrapping electric heating units around the reactorand covering it with a glass cloth insulation. The heating elements arecontrolled by transformers (not shown), as is conventional practice. Thetemperatures in various sections of their reactor may be read on atemperature indicator (not shown) interconnected with the thermocouplesTC TC TC and T0,.

In addition to the electric heating units wrapped around the reactor,another temperature controlling means is provided by means of a pressurecondenser system 11 which includes a cold finger condenser portion 13extending from an upper portion of the reactor chamber into the lowerportion thereof. A thermostatic fluid is placed in the cold finger andthe boiling point of this fluid is controlled by means of nitrogenpressure exerted on the system from the tank indicated.

Dry air from supply line 14 is divided into two lines 15 and 16 whichpass through rotameters 17 and 18, respectively, depending on whetherthe syringe pump 19 or carburetor 20 is used for hydrocarbon feed. Theregulated air and hydrocarbon vapor streams are preheated in a preheater21, which normally may be an electric element preheater. Air from theline 15 through the rotameter 17 enters the preheater 22 as primary air,and the hydrocarbon is introduced from the syringe pump 19 into thepreheater along with the secondary air from line 16 through rotameter18. The feed to the preheater is provided either as a liquid or a vapor,depending on whether the pump 19 or the carburetor 20 was used. Wherethe feeds are liquids or solids, they may be fed through a jacketedcarburetor equipped with a heater.

The products of the reaction are passed from the reactor through outlet3 into a glass U-tube air condenser system 23, bafile condensers 24, andgenerally through a series of three Dry Ice acetone bubbler traps 25connected in series. The exhaust from the Dry Ice traps is measured in awet test meter 26.

The catalyst used in the experiments set forth in Table 1 below iscommercially available Davison 902 vanadia catalyst screened to between100 +200 mesh, and which was preactivated in a ceramic tube for abouttwelve hours held at about 430 C. with a low flow of air thereacross todrive off the undesirable mineral acids and to further prevent corrosionof the oxidation apparatus. The composition of this Davison 902 catalystis approximately vanadia, 33% potassium sulfate and 55% silica. Thiscatalyst was conveniently diluted with inert Davison activated silica inapproximately the same mesh size. The hydrocarbons oxidized in the testare set forth in Table 1 and these consisted of pure2,3-dimethylnaphthalene and pure l-methylnaphthalene.

OPERATING PROCEDURE FOR FLUID CATALYST BEDS The fluid-like character ofthe fine catalyst permits ready addition of it to the reactor, as forexample, from a weighed plastic squeeze bottle and it is readily removedby siphoning techniques without interrupting operating conditions. Priorto an actual run, an additional two hours activation time at about 375and at about 500 6 liters of air per hour air flow in the reactor willbring the catalyst to temperature equilibrium with the reactor at aboutoperating conditions. After such prescribed time and when the reactortemperature is essentially uni-' form in the range of 300400 C. a runmay be commenced. The temperatures during these runs must be carefullycontrolled by adjustment of the transformers heating the reaction tubeand by adjusting the nitrogen pressure on the cold finger condenser. Thehydrocarbon feed is charged to the feed device and the run completedwith a predetermined amount of hydrocarbon.

The total product trapped in the air condenser, the

baflie condenser, and the acetone traps from each run- ExampleI.-Oxidati0n of 2,3-dimethylnaphthalene to naphthalene About 219 ml.(212 g.) volume of Davison 902 fluid vanadia catalyst was activated inthe apparatus at 430 C. for 2 hours at an air flow of 500 liters perhour. The fluid bed reactor was controlled at 375 C., and aftertemperature equilibrium was obtained, the syringe pump was heated andthen filled with pure 2,3-dimethylnaphthalene. The air and feed rateswere set to approxmately liters of air per gram of feed, and this gaveabout 0.4 second contact time of the vapor with the catalyst. runcontinued for a period of about 45 minutes. A total of 4.4 grams of2,3-dimethylnaphthalene was fed through the reactor during this time ata rate of about 7.475 grams per hour. A total of 2.82 grams ofcondensable reaction product mixture was collected in the traps.

Calculated reaction conditions for the completed run were weight/hourlyspace velocity of 0.0343 kg. per liter-hour; gas/hourly space velocitiesof 4,560 liters per liter-hour; air-to-feed ratio of 133 liters of airper gram feed; and a contact time of 0.414 second.

Elution chromatography of about 1 gram sample of the reaction productmixture over chromatographic alurnina with eluting solvent mixtureranging from petro- 'leum ether through carbon tetrachloride,chloroform, and finally acetone yielded 23 fractions which wereevaporated to dryness in tared flasks. A total of about 12.3% purenaphthalene was recovered from the product. This corresponds to aconversion of about 7.9 weight percent or 8.8 mole percent per pass.

The recovered naphthalene had a melting point of 80.l-80.7 C. A completeanalysis of the material for naphthoquinone, phthalic anhydride, andmaleic anhydride indicated a total hydrocarbon content of less than12.9% by difference, and obviously most of this material is in therecovered naphthalene.

Examples 2 through 20.Oxidati0n of I-methylnaphthalene t'o naphthalene Atotal of 18 runs are summarized in Table I wherein purel-methy-lnaphthalene was oxidized over commercial Davison 902 fluidvanadia, and the combinations of operation ranges include temperaturesin the range of 300--351 0., contact times ranging from 0.101 to 0.761second and an air-feed ratio of 4.71 to 20.20 liters of air per gram offeed. The yields of naphthalene range from 0 to about 8.1 weight percentconversion.

Operating the apparatus essentially is set forth in Example 1, and atthe conditions set forth, the following table summarizes runs 3 through20.

The air and feed flows were commenced and the TABLE I.-VAPOR-PHASEOXIDATION OF I-METHYL- NAPHIHALENE TO NAPHTHALENE OVER FLUID VANADIAExperimental Naphtha- Oonditions lene Re- Naphthalene Yield covcryExample Wt.per- T.( C.) t Sec Alf cent of Wt. per- Mole (l./g.) totalcent a percent b I-LO.

A. PRELIMINARY 2 EXPERIMENTAL DESIGN B. ATTEMPT TO APPLY STEEPEST ASCENTTECHNIQUE WITH THREE VARIABLES $3 on about 5.5 ml. of preignitedalundum. The bypass valves 40 are arranged to pass feed and air streamsthrough the microreactor or to bypass the microreactor. The dryingcolumn 33 was a packed column of mixed ascarite and magnesiumperchlorate to remove most of the carbon dioxide, water and organicacids which might interfere with the analysis of hydrocarbon from thetwo meter separation column 34 which contains silicon oil on firebrick.The hydrocarbons which emerged from the separating column are detectedand assayed by detector cell 35 which was contained in a bridge circuitof an electronic chart recorder. The various feed mixtures were used forcalibration by bypassing the microreactor to obtain the characteristicretention time, separations, and the peak areas for the naphthalene anda l-methylnaphthalene. The reaction product peak areas were used todetermine the total hydrocarbon recovery and the amounts of naphthaleneand l-methylnaphthalene in the recovered hydrocarbons. A pressuredifferential of about 4 p.s.i.g. across air lines 36 and 37 wasmaintained at a fixed rotameter 32 air flow setting by means of fiowcontrol valves 33 at the sample injection block 41. Hydrocarbon samplesof 0.001 to 0.010 ml. were injected into the injection block 319 0.18910. 03 0. 26 0. 0. 2s 1 3 0-191 11-64 0.36 0440 40 by means ofcalibrated microdippers. Tne metal ox- 00 20'20 25 ides investigated ascatalysts for the production of naphthalcne accordin to this method arelisted in Tabe II. 0. APPLICATION OF STEEPEST ASCENT TECHNIQUE g WITI-IONLY TWO VARIABLES TABLE II.MTATERIALS INVESTIGATED 324 0.263 7.34 13.24. 63 5.14 Catalyst, Metallic Oxides Selectivity for Com- Production ofN 325 0.260 11.94 28.0 0.31 0.34 bustion N/l-MN from l-MN 326 0. 7357.49 27.2 2.90 3.21 325 0. 761 12. 55 17. 0 3. 50 3. 39 324 0. 14.9 0.7s 7. 09 8. 03 8.96 325 0.154 5. 30 12. 32 4.10 1. 55 321 0. 154 0. 5519. 22 4. 93 5. 47

1 a wti agrcent yield wt.naphthalenelwt. feedwt. l-mcthylnaphthalafolepercent yield wt. percent yield X gmw l-mcthylnaphthalenc/ gmwnaphthalene.

For Example 18 the l-methylnaphthalene, 71 1.6160, was prepared byfractional distillation and its isomeric purity confirmed by gas-liquidchromatographic analysis. The fluid bed reactor was brought totemperature equilibrium at about 325 C., and the preactivated fluidcatalyst consisted of about 36.7 ml. (35.6 g.) of Davison 902 fluidvanadia catalyst at 100+200 mesh and about 100 ml. of Davison silica asa diluent. The l-methylnaphthalene was pumped into the apparatus at arate of about 60 grams per hour and the air flow regulated at about 360liters per hour based on standard temperature and pressure. The run wascontinued for a period of about one hour. The results are as set forthin Table I.

FIXED CATALYST BED A microreactor technique combined with gas-liquidchromatographic apparatus was used to investigate the selectivecatalytic oxidation reactivities of a large number of essentially purereagent grade metal oxides for the production of naphthalene. Over 1400runs were conducted with this technique and of the severaLfeeds studied,there were included a mixture of 25 weight percent naphthalene-75%substantially pure I-methylnaphthalene; a mixture of substantially pure1,2- and 1,7-dimethylnaphthalenes; an aromatic extract from lightcatalytic cycle oil; toluene; l-naphthaldehyde; l-naphthyl alcohol; and1- naphthoic acid.

One scheme of the apparatus for such a microreactor technique is shownin FIG. 2 wherein all the apparatus, with the exception of the aircylinder, was contained in two air baths of gas-liquid chromatographicapparatus controlled at 200 C. The microreactor tube 31 consisted of astainless steel tube of about 0.63 centimeters ID. and about 40 cm.long. The tube 31 is covered by an electric heater 32 controlled by atemperature recorder-controller, as set forth above, controllable in theregion of 300-600" C. A weighed samped of about 0.5 ml. of finelypulverized metal oxide was uniformly dispersed Notes:

a. Alundurn, an alumina/silica, gave little combustion at anytemperature and was used as a support for testing the other oxides.

b. Silver oxide decomposes at 300 C. but naphthalene was produced overthe decomposition product, which was probably the metal.

0. Antimony pentoxidc decomposes to 813204 at 380 C. and adsorbs allfeed, yielding a new compound (unidentified) at 200 C. Completecombustion was noted at 300 C.

It is noted from Table I1 above that a substantial portion of the metaloxides investigated were found to be etiective in significant selectivecatalytic oxidation of the 25 weight percent naphthalene-75 weightpercent 1- methylnaphthalene feed mixture at temperatures substantiallybelow spontaneous ignition temperature of 559 C. as indicated by theplus marks of column 2 in Table II. Reagent grade vanadia was found tobe more selective for the purpose than commercial Davison 902 vanadiacatalyst, for example. Further, stable oxides of zinc,

silver, cadmium, indium and bismuth were found to be more selective thanthe reagent grade vanadia.

The results with the three most selective oxides of cadmium oxide,bismuth oxide, and indium oxide are summarized in FIG. 3. It is to benoted that if a catalyst manifested no selectivity, the composition ofthe recovered hydrocarbon remained substantially constant at the feedcomposition.

All of the metal oxides listed in Table III were also investigated fortheir production of naphthalene from pure l-methylnaphthalene. Theproduction of naphthalene by these oxides is indicated in column 3 ofTable III by the plus marks. The most effective catalysts for theproduction of naphthalene from l-methylnaphthalene were found to becadmium oxide, bismuth oxide, indium oxide, and silver oxide. Thisproduction of naphthalene was achieved in the range of Soil-600 C. atabout 0.1-2 seconds contact time at about 0.1 to 5 liters per gramair-to-feed ratios. Note that these conditions are considerablydifferent from those of thermal or catalytic hydrocraclzing.

The carrier gas during one experiment was changed from air to nitrogen,and this confirmed the necessity of oxygen for the dealhylation since nonaphthalene was produced with nitrogen as the carrier stream. Additionalexperiments were run to determine the eltect of oxygen concentration onthe reaction, and this is shown in FIG. 4 wherein the upper line showsthe conversion of l-methylnaphthalene to naphthalene in a oxygen carrierand in the lower curve of air (containing normal oxygen). The conversionis shown at different temperatures over 3.4-4.1 weight percentcadmiasilica (explained below).

A very reactive form of cadmium was prepared by the addition of cadmiumnitrate to a solution of sodium silicate followed by coprecipitationwith an acid. The recovered catalyst was very reactive and moreselective than cadmium oxide reagent.

Examples 2139.Oxidati0n of J-methylnaphthalene over cadmium oxidel-methylnaphthalene was oxidized over cadmium oxide to produce directlynaphthalene, and Example 31, detailed below, is typical of this set ofruns. In this case, cadmium oxide was utilized for the selective vaporphase oxidation of 25 weight percent naphthalene-75 weight percentl-methylnaphthalene feed in air at a temperature range of 300-600 C.

In accordance with the procedures for the microreactor given above, themicroreactor tube was filled with 0.5 ml. (0.400 g.) of finelypulverized cadmium oxide mechanically dispersed on about 5.5 ml. of -+60mesh alundum support. The microreactor was brought into temperatureequilibrium at about 525 C. by means of a thermocontroller.

A sample of 0.007 ml. of essentially pure l-methylnaphthalene wasinjected into air which was flowing at a rate of about 17.5 ml. perminute into the microreactor. The estimated reaction conditions areabout 525 C.; O.22 seconds contact time; and 0.1 to 5 liters of air tograms of feed. The reaction product mixture gave a chromatograph curveconsisting of carbon dioxide, water, and a naphthalene, in addition tounconsumed l-methylnaphthalene. An analysis of the curve shows that therecovered hydrocarbon amounted to about 58.5 weight percent of thel-methylnaphthalene feed, and of this 41.0 weight percent wasnaphthalene and 59.0 weight percent was l-methylnaphthalene. Theconversion to naphthalene was about 24.0 weight percent per pass basedon the total l-methylnaphthalene feed. The ultimate yield was found tobe 36.6 weight percent or about 40.6 mole percent naphthalene based onthe actual amount of the 1- methylnaphthalene consumed.

The results of the oxidation over this particular catalyst aresummarized in Table IV. This table shows high sel0 lectivity of thecadmium oxide, and it was found by experimentation that cadmium oxide onan inert support exhibits better selectivity than the same amount ofcadmium oxide and support disposed as a separate zone or a slug in thereactor.

TABLE III.SELECTIVE OXIDATION OF l-METHYLNAPH' THALENE TO NAPHTHALENEOVER OADMIUM OXIDE Conditions Hydrocarbon Recovery Example Feed Wt. Wt.'lmf 0. Percent Percent Wt. Wt. N l-MN Percent Percent N l-MNN=Naphthalene l-MN =1Mcthy]naphthalene Other active forms of cadmium maybe prepared by various chemical methods from decomposable salts orcompounds of cadmium, e.g., cadmium nitrate, sulfite, carbonate, acetateand hydroxide. The more active and selective forms of the cadmium arethose on various supports such as alundum, silica, silicon carbide andceramic materials which may be prepared by evaporative or vacuum imprenation techniques with aqueous solutions of cadmium salts on thesupports. Such catalysts, after being deposited on the support, aredried and treated at about 600 C. for two hours to decompose the cadmiumcompounds into the oxide.

One very active cadmium composition is produced when cadmium isprecipitated in the presence of sodium silicate by the addition of anacid, after such precipitation which is recovered it is subsequentlyrinsed, and dried at 600 C. for about two hours. The catalyst recoveredfrom this process is white in appearance. For purposes of thisapplication such a catalyst is called cadmia-silica. The composition ofthe material obviously varies and is dependent on the amount ofingredients admixed together.

Example 40.Preparati0n o a cadmia-silica catalyst A solution of about 45ml. of water glass in about 855 ml. of distilled water was stirred in abeaker. To this solution was added a solution of about 2.4 grams ofcadmium nitrate in ml. of distilled water which was added drop-wise overa period of about ten minutes to produce a milky suspension. Four dropsof phenophthalein were added and a third solution of aqueous nitric acidwas added drop-wise with vigorous stirring over a period of about tenminutes. The pH of the final solution was about 6 as determined byindicator paper. The resultant mixture was then poured into centrifugebottles and centrifuged, a supernatant solution decanted and the gelmixed and rinsed with portions of aqueous 10% ammonium nitrate and theresultant product dried for about 16 hours at 138 C. and then ignited atabout 600 C. for two hours in a muifie furnace. The product was thenscreened to a -30+60. A sample of the catalyst was shown by emissionspectroscopy to contain 3.4 weight percent cadmia. Diffraction X-rayanalysis indicated the material to be of a rather amorphous structure.

1 1 SELECTIVE OXlDATION Following the procedure given above, themicroreactor tube was filled with about 6.0 ml. (3.0 g.) of thiscatalyst. The operating procedure was similar to that described forExample 18 above. The results of the oxidation using this catalyst aresummarized in FIG. 4 wherein the ultimate Weight percent of naphthaleneyields were plotted for a temperature range of 400-600 C. In this case,two carrier gas streams were employed, as pointed out above, one at 20%oxygen (air) and the other at 10% oxygen, which is air diluted with anequal volume of nitrogen. The results obtained with these differentoxidation mixtures are presented on curves A and B of FIG. 4. It isnoted that better yields are obtained at the lower temperatures and witha lower oxygen concentration over this particular catalyst.

Examples 41-48.-Selective oxidation of various feeds Following theprocedure of Example 18, the microreactor-gas-liquid chromatographictechnique was used to investigate the selective oxidation of severalfeeds other than the monomethylnaphthalene. In Examples 41 and 42, theproduction of monom-ethylene and naphthalene are demonstrated by theselective oxidation of 1,7- and 1,2- dimethylnaphthalene (1,7-DMN and1,2-DMN). Example 43 shows the oxidation of an aromatic extract of lightcatalytic cycle oil from a catalytic cycle oil in the boiling range or"490-525 C. This feed, which contains various alkylaromatic compositions,Was selectively oxidized to produce monomethylnaphthalene andnaphthalene. Example 44 shows the selective oxidation of 1-naphthaldehyde to produce naphthalene, and in Examples 45 and 46 decalinand tetralin, respectively, were oxidized to produce naphthalene.Example 47 shows the results of oxidizing toluene to produce benzene,and Example 48 shows the production of benzene and toluene from theoxidation of xylene. The catalyst for Examples 41a, 42a and 43 wascadmium oxide dispersed on alundum, and for the remainder of theexamples in the table, the catalyst is cadmium coprecipitated withsilica, as described above. The results of these tests are shown inTable V, given below.

TABLE IV.-OXIDA'lION OF VARIOUS FEEDS TO I-IYDROCARBONS ExampleConditions Reaction Products Feed Oxidant 1,7-DMN.

N, MMN, DMN. N, MMN, DMN. Naphthalene.

Do. Benzene. Benzene, toluene.

N=naphthalcne. MMN=monon1ethylnaphthalcne. DMN dimethylnaphthalenc.

Examples 4966.C0l1versi0n f l-methylnaphtlmlene where a is the weightpercent yield of naphthalene, x is the log (Wt. percent CdO) on thecatalyst, y is the log (Wt. percent 0 in the carrier gas stream, and A,

12 B, C, D, E,'and F are empirical constants. The conversion data ateach temperature were fitted to a seconddegree polynomial equation ofthe general form, (2) 6:1 1+Bx+Cy+Dx +Ey -i-Fxy where B is the weightpercent conversion to naphthalene, x is the log (wt. percent CdO) on thecatalyst, y is the log (wt. percent 0 in the carrier gas stream, and A,B, C, D, E and F are empirical constants. The yield data at 400 C., withthe exception of Example 50, were titted to a particular polynomial to:5 .4 wt. percent; the conversion data at 400 C., with the exception ofEx ample 50, were fitted to a particular polynomial to :31 wt. percent.All of the yield data at 450 C. were fitted to a particular polynomialto :3.8 wt. percent. All of the conversion data at 450 C. were fitted toa particular polynomial to i2.8 Wt. percent.

These experimental results at 40 C., and 450 C. are graphicallyrepresented in FIG. 5 and FIG. 6, respectively. The data points areindicated by the circled numbers and refer to the key in Table V. Theisoconversion and isoyicld contours were obtained from graphic solutionsof the empirical polynomial expression which obtained from least squarefits of each group of data. On inspection of the regions of overlap forthe isoconversion and isoyield contours, it is apparent that the morefavorable reaction conditions at 400 C. are over about 2-5 wt. percentCdO, with about 525 wt. percent 0 in the carrier gas stream, yieldingabout from 30 to 62:5 wt. percent naphthalene at conversions of about2025:L3 wt. percent, and at 450 C., over 2-8 wt. percent CdO, with about5-25 wt. percent 0 in the carrier gas stream, yielding about from 32 to58i4 wt. percent naphthalene at conversions of about 20-25i3 Wt.percent.

It is thus apparent that selective oxidative dealkylation of higherhomologous alkyl substituted hydrocarbons is a feasible and economicalprocess for producing lower member of such a series. It is, furthermore,a valuable process for recovering parent aromatic hydrocarbons from amixture of alkyl substituted compositions of such parent compounds.While the invention has been described by reference to specificexamples, there is no intent to limit the spirit or scope of theinvention to the details so set forth, except as defined in thefollowing claims.

TABLE V.--EFFECTS OF REACTION VARIABLES ON THE SELECTIVE OXIDATION OFl-METHYLNAPI-ITHALENE TO NAIHTHALENE Conditions Results Key No. Exampleon Figs. Wt. Per- Wt. Per- No. 5 & 6 Temp, Wt. Wt. cent Con cent Yield0. Percent Percent version to of Naphtha- O2 CdO Naphthalone lens Weclaim:

1. A selective dealkylation oxidation process for the production oflower molecular weight aromatic hydrocarbons from higher molecularweight alkyl substituted aromatic hydrocarbons which comprisescontacting for a limited time a vaporous mixture of such alkylsubstituted aromatic hydrocarbons and a gas containing from 1 to 50% ofoxygen by weight with a fluidized bed of an oxidation catalyst selectedfrom the group consisting of inorganic insoluble salts of cadmium andinsoluble oxides of silver, zinc, cadmium, indium, and bismuth, in atemperature range of from 300-600 C. and at a gas-tofeed ratio of from0.5 to 10 liters per gram whereby to limit the residence of thehydrocarbon over the catalyst at from .05 to seconds.

2. A- process according to claim 1 in which the oxidation catalyst is aninsoluble, inorganic cadmium salt.

3. A process according to claim 1 in which the oxidation catalyst iscadmium silicate.

4. A process according to claim 1 in which the oxidation catalyst iscadmium oxide.

5. A process according to claim 1 in which the oxidation catalyst is aco-precipitated product of a soluble cadmium salt and a water glasssolution.

6. A process according to claim 1 in which the oxidation catalyst isbismuth oxide.

7. A process according to claim 1 in which the oxidation catalyst isindium oxide.

8. A process for the production of naphthalene from l-methylnaphthalenewhich comprises contacting for a limited time a vaporous mixture of suchl-methylnaphthalene and a gas containing about 5-25 weight percent ofoxygen with an oxidation catalyst selected from the group consisting ofinorganic in soluble salts of cadmium and insoluble oxides of silver,zinc, cadmium, indium and bismuth, at temperatures of between 400-450"C., the ratio of gas to feed being on the order of from 0.5 to litersper gram whereby to provide a residence time of the aromatic hydrocarbonwith the oxidation catalyst of from 0.1 to 2 seconds, and separating theproduced naphthalene from the mixture.

9. A process according to claim 8 in which the oxidation catalyst iscadmium oxide.

10. A selective oxidation process for the production of lower alkylhomologs of benzene and benzene from higher molecular weight alkylsubstituted benzenes which comprises contacting for a limited time avaporous mixture of such alkyl substituted benzenes and a gas containingfrom 1 to oxygen by weight with a fluidized bed of an oxidation catalystselected from the group consisting of inorganic insoluble salts ofcadmium and insoluble oxides of silver, zinc, cadmium, indium, andbismuth in a temperature range of from 300-600 C. and at a gasto-teedratio of from 0.5 to 10 liters per gram whereby to limit the residencetime of the hydrocarbon over the catalyst of from 0.05 to 5 seconds.

References Cited in the file of this patent UNITED STATES PATENTS2,301,735 Melaven et a1 Nov. 10, 1942 2,343,450 Free et al. Mar. 7, 19442,351,793 Voorhees June 20, 1944 2,370,541 James Feb. 27, 1945 2,470,411Corner May 17, 1949 2,474,002 Levine et al June 21, 1949 2,565,627 PryorAug. 28, 1951 2,810,764 Steadman et a1. Oct. 22, 1957 FOREIGN PATENTS159,508 Great Britain Aug. 28, 1922 649,999 Great Britain Feb. 7, 1951OTHER REFERENCES Chemical Abstracts (I), vol. 41, page 5465f (1947).Chemical Abstracts (11), vol. 43, page 7916;; (1947).

1. A SELECTIVE DEALKYLATION OXIDATION PROCESS FOR THE PRODUCTION OFLOWER MOLECULAR WEIGHT AROMATIC HYDROCARBONS FROM HIGHER MOLECULARWEIGHT ALKYL SUBSTITUTED AROMATIC HYDROCARBONS WHICH COMPRISESCONTACTING FOR A LIMITED TIME A VAPOROUS MIXTURE OF SUCH ALKYLSUBSTITUTED AROMATIC HYDROCARBONS AND A GAS CONTAINING FROM 1 TO 50% OFOXYGEN BY WEIGHT WITH A FLUIDIZED BED OF AN OXIDATION CATALYST SELECTEDFROM THE GROUP CONSISTING OF INORGANIC INSOLUBLE SALTS OF CADMIUM ANDINSOLUBLE OXIDES OF SILVER, ZINC, CADMIUM, INDIUM, AND BISMUTH, IN ATEMPERATURE RANGE OF FROM 500-600*C. AND AT A GAS-TOFEED RATIO OF FROM0.5 TO 10 LITERS PER GRAM WHEREBY TO LIMIT THE RESIDENCE OF THEHYDROCARBON OVER THE CATALYST AT FROM .05 TO 5 SECONDS.